Comparing to retail is not apples to apples. The overall margins on Amazon tend to be lower across the board. So, yes, there's a problem with comparing directly with retail in general. Amazon is taking on distributor costs, but they aren't really doing anything to reduce manufacturer costs. Manufacturers still need an assembly line, warehousing, shipping (to get it to Amazon), & running their business... maybe they're not getting any profit, but that's the problem we're talking about.

While amazon is covering their own warehouse & fulfillment shipping costs, that's really that different from costs normally borne by retailers who have warehouses and handle delivery to their retail outlets.